I need a little help on this one. I built a 'sun room' addition and will now add a new baseboard heat zone to my boiler. I went to slantfin.com and downloaded their heat loss calculator and it determined that I need 41 feet of the high output baseboard to adequately heat the room. The room is 28' x 16' with three outside walls. The ceiling height is 8' around the perimeter and goes to 12' in the center (vaulted). For the calculator I chose an average of 10'. The three outside walls are all Andersen permashield casement windows (it's almost all glass). Does this seem correct that I would need so much radiation, or could I have assumed something wrong in the calculator? Thanks.

Frank